1. Field of the Invention
The present invention relates to an apparatus and process for generating a mixed multi-component vapor. More particularly, the present invention relates to an apparatus and process for generating a mixed multi-component vapor from a mixed multi-component liquid comprising two or more liquid components different in boiling temperature from each other and soluble in or compatible with each other, by using a thin film evaporator and a forcedly liquid-circulating line connected to the evaporator, the resultant mixed multi-component vapor having a composition very similar to that of the mixed multi-component liquid, and the thermal deterioration of the components being very low.
The present invention includes an apparatus and process for producing a gas phase catalytic reaction product by utilizing the mixed multi-component vapor-generating apparatus and process, respectively.
2. Description of the Related Art
It is well known that a mixed vapor of a plurality of compounds different in boiling temperature from each other can be prepared by separately generating vapors of the compounds from each other, and mixing the resultant vapors in a derived mixing proportion in a mixing vessel.
This conventional mixed vapor-preparing method is disadvantageous in that when at least one compound has a high boiling temperature, and thus must be vaporized at a temperature higher than the high boiling temperature of the compound, the high temperature vaporization applied to the component causes a thermal deterioration of the compound.
Also, it is known that a mixed multi-component vapor can be prepared by preparing a mixture of the components in the state of liquids, and applying a vaporization procedure to the mixed multi-component liquid in a conventional evaporator. When the boiling temperature of the components are different from each other, the composition of the resultant mixed multi-component vapor is different from that of the starting mixed multi-component liquid. The larger the difference in boiling temperature between the components, the larger the difference in composition between the starting mixed multi-component liquid and the resultant mixed multi-component vapor. Usually, the content of a component having a low boiling temperature in the resultant mixed multi-component vapor is higher than it in the starting mixed multi-component liquid.
The conventional apparatus and method for generating the mixed multi-component vapor are disadvantageous in that a mixed multi-component vapor having a desired composition cannot be obtained from a mixed multi-component liquid at a high stability with a high degree of reproducibility under practical conditions.
For example, in a process for producing a monoalkyl ether of a dihydric phenolic compound by a catalytic reaction of a dihydric phenolic compound, for example, catechol, with a lower alkyl alcohol in the gas phase in the presence of a phosphorus-containing catalyst, as disclosed in Japanese Unexamined Patent Publication No. 3-115,244, No. 4-74,149 and No. 4-341,345, a mixed vapor of catechol and the lower alkyl alcohol is fed into a reactor packed with the catalyst to react catechol with the lower alkyl alcohol. In this method, catechol is thermally deteriorated during the mixing and reacting procedures of the mixed vapor to a certain extent, and thus the reaction product contains undesirable by-products, particularly compounds having high boiling temperature. Therefore, there has been a strong demand of removing the above-mentioned disadvantages of the conventional apparatus and method.
For example, there has been attempted a method of preparing a mixed vapor by vaporizing catechol alone and mixing the resultant catechol vapor with a vapor of a lower alkyl alcohol. In this attempt, catechol must be vaporized at a temperature certainly higher than the boiling temperature of catechol and thus was thermally deteriorated to a certain extent. Therefore, this method is not appropriate in practice. In another attempted method, a mixed liquid of catechol and the lower alkyl alcohol was prepared, and then vaporized in an evaporator to provide a mixed vapor. However, in this method, it was found that since a difference in boiling temperature between catechol and the lower alkyl alcohol is large and thus in the resultant mixed vapor, the content of the lower alkyl alcohol is significantly higher than that in the starting mixed liquid. Therefore, in this method, it was very difficult to obtain a mixed vapor having a desired composition from a corresponding mixed liquid by a single evaporation procedure. Namely, this method was unsuccessful in practice.
An object of the present invention is to provide an apparatus and process for generating a mixed multi-component vapor having a desired composition by evaporating a mixed multi-component liquid having a composition very similar to that of the mixed multi-component vapor, with high reproducibility and high stability, while preventing or restricting undesirable thermal deterioration of the components.
Another object of the present invention is to provide an apparatus and process for generating a mixed multi-component vapor having a desired composition from a mixed multi-component liquid having a composition very similar to that of the mixed vapor, which mixed multi-component vapor can be directly subjected to a reaction, in the gas phase, of the multi-components with each other.
The above-mentioned object can be attained by the apparatus and process of the present invention.
The apparatus of the present invention for generating a mixed multi-component vapor, comprises
a thin film evaporator having a feed inlet through which a mixed multi-component liquid comprising two or more liquid components different in boiling temperature from each other and soluble in or compatible with each other is fed into the evaporator and a delivery outlet through which a resultant mixed multi-component vapor is delivered from the evaporator;
a feed line for feeding the mixed multi-component liquid, connected to the feed inlet of the evaporator;
a delivery line for delivering the resultant mixed multi-component vapor, connected to the delivery outlet of the evaporator; and
a forcedly liquid-circulating line having a circulation inlet end connected to a delivery side end portion of the evaporator, a circulation outlet end connected to a feed side end portion of the evaporator and a liquid transporting means arranged between the circulation inlet end and the circulation outlet end of the circulating line, whereby a non-evaporated portion of the mixed multi-component liquid is forcedly circulated through the circulation inlet end, the liquid transporting means and the circulation outlet end of the circulating line.
The process of the present invention for generating a mixed multi-component vapor comprises the steps of:
feeding a mixed multi-component liquid comprising two or more liquid components different in boiling temperature from each other and soluble in or compatible with each other into a feed side end portion of a thin film evaporator;
evaporating the mixed multi-component liquid in the evaporator;
and delivering a resultant mixed multi-component vapor from a delivery side end portion of the evaporator,
wherein the non-evaporated portion of the mixed multi-component liquid present in the evaporator is forcedly circulated through a circulating line having a circulation inlet end connected to the delivery side end portion of the evaporator, a circulation outlet end connected to the feed side end portion of the evaporator, and forcedly liquid-transporting means located between the circulation inlet end and the circulation outlet end of the circulating line, by withdrawing the non-evaporated portion of the mixed multi-component liquid from the delivery side end portion of the evaporator through the circulation inlet end and returning the withdrawn non-evaporated portion of the mixed multi-component liquid into the feed side end portion of the evaporator through the forcedly liquid-transporting means and the circulation outlet end of the circulating line, thereby to promote the simultaneous evaporation of the two or more liquid components and the generation of a mixed multi-component vapor in which the two or more components are present in substantially the same composition as that of the mixed multi-component liquid.
By utilizing the apparatus of the present invention, a gas phase catalytic reaction product can be produced by an apparatus which comprises:
the mixed multi-component vapor-generating apparatus of the present invention, and
a gas phase catalytic reactor connected to the mixed multi-component vapor-generating apparatus through the mixed multi-component-delivery line, and having a delivery line for delivering a resultant reaction product-containing gas fraction from the reactor.
Also, by utilizing the process of the present invention, a gas phase catalytic reaction product can be produced by a process which comprises the steps of:
generating a mixed multi-component vapor in accordance with the process of the present invention,
subjecting the mixed multi-component vapor to a gas phase catalytic reaction procedure, and collecting the resultant reaction product-containing gas fraction.